1. Field of the Invention
The present invention relates to a portable terminal device and a communication control method, and particularly relates to a portable terminal device having a local built-in radio communication device and a communication control method for controlling such a portable terminal device.
2. Description of the Related Art
Recently, with the spread of cellular phone system, various techniques have been developed to accomplish communications between networks and portable terminal devices. It is known to design a portable terminal device as a personal digital assistant (PDA) provided with a built-in cellular phone which can establish a connection with a network. It is also known to connect a personal digital assistant to a cellular phone for providing communications with a network. On the other hand, a car-mount navigation system with hands-free capability is known. For hands-free operation, in which a phone conversation may be made without holding a handset, a car-navigation system is wire-connected to a cellular phone.
In order to provide communication capability to a known portable terminal device, the portable terminal device may be connected to a cellular phone or may be provided with a built-in communication device. Conventionally, the portable terminal device having a built-in communication device is further provided with a handset to enable phone conversations.
Another way of providing communication capability to a portable terminal device having a built-in communication device is to connect it to hands-free capability of the car-mount navigation system. However, the portable terminal device must be taken out of a storing location such as a bag or a pocket of a jacket and connected to a car-mount terminal such as a car navigation system. When the user leaves the vehicle, the portable terminal device must be separated from the car navigation system and stored in the storing location such as a bag or a pocket of a jacket. This is considerably troublesome to the user. Also, if the user forgets to remove the portable terminal device from the car navigation system and leaves the vehicle, the portable terminal device cannot be used for making phone conversations.
Also, with the spread of portable terminal devices having built-in communication devices, a so-called push-type data distribution service has also become wide-spread in which data is distributed from a server connected to a wide-area network (WAN). Conventionally, the push-type data distribution service has been realized using radio communication devices dedicated for data communication.
In order to make use of the push-type data distribution service using a conventional portable terminal device, it is necessary to mount a radio communication device dedicated for data communications. This causes problems since the handling of voice and data is rather complicated.
Further, if there are both a normally used handset and a hands-free function of the navigation system, there are two means for making phone conversations (voice input/output means). This causes a problem since it may confuse the user.